In the United States there are at least 3 major broadcasting networks (e.g. ABC, NBC, and CBS), and also a number of cable service networks (e.g. HBO, ESPN, Cinemax, etc.), each of which distributes broadcast television programs throughout the country. Many viewers tend to associate their favorite television programs with the networks that carry them. A common problem is that there are so many channels available that it is difficult for a viewer to remember which channel number corresponds to which network. For example, in some areas of the country a viewer has access to as many as 40 channels. Thus, tuning by channel number, although widely used, may not be desirable in these situations.
Furthermore, in the hotel/motel environment, the visitor is typically unfamiliar with local channel numbers. When the visitor wishes to watch a favorite program on a known major network, he may have difficulty locating the proper local channel owned by, or affiliated with the major network. Compounding this problem is the fact that it is common practice among cable companies in the United States to remodulate broadcast signals to different channels of the RF spectrum than those channels which they normally occupy. Unfortunately, this also has the effect of confusing the viewer because, for instance, UHF channel 29 may be remodulated (down converted) to occupy the frequency space of, for example, VHF channel 9. Thus, even if a viewer happened to know that the FOX Broadcasting Network corresponds to channel 29 (as it does in Philadelphia), the viewer may still have difficulty locating his desired programs when the signals transmitted by channel 29 are in fact received on cable channel 9.
A common solution to this problem is to distribute channel conversion charts to cable subscribers so that they may locate the proper cable channel, given the standard broadcast channel, from a printed television schedule. This solution is less than satisfactory because of the relatively large number of available channels.
Additionally, a problem arises because the channel numbers assigned to the major networks are not the same across the country. For example, the National Broadcasting Company (NBC) broadcasts on channel 4 in New York City, N.Y., on channel 3 in Philadelphia, Pa., on channel 5 in Cincinnatti, Ohio, and on channel 11 in Dayton, Ohio. Because television manufacturers cannot know in advance in which viewing areas their receivers will be operated, it is not possible to preprogram the tuning system at the factory to select a particular channel in response to the selection of a network's name.
Efforts have been made by manufacturers to relate channel numbers to network names. For example, it is known from GRUNDIG television receiver CUC-2400 to display on the television screen a station identification label (previously entered by the user) whenever a channel is selected. However, the user must still somehow remember which channel is assigned to which network, because channel selection in this system is by channel number.
Thus, it is desirable that television manufacturers provide remote control handunits which allow viewers to select the channels by name.
A tune-by-label system is known from U.S. Pat. No. 4,706,121 (Young). However, Young provides no means by which the user can enter labels of his own choosing, either for display or for selecting a channel. In Young, the labels are provided by a broadcaster, as part of a TV schedule transmitted to an in-home tuner controller. The labels, such as HBO and ESPN, are displayed in a menu for selection by the user. Such a system requires costly and complex circuitry. Perhaps, more importantly, it requires the cooperation of broadcasters to dedicate limited spectrum space to the transmission of schedule information.
Given the fact that a tune-by-label system is desirable, the memory requirements of such a system need be addressed. Specifically, the memory should be non-volatile so that it retains a user-entered label list, in the event of a power failure. However, a non-volatile memory, such as EEPROM (electrically erasable programmable read only memory), may require a relatively long "memory write" (storage) time (on the order of 40 ms per byte). It also requires a relatively long "memory read" time (on the order of 500 .mu.S per byte). A search of a label list for a match is required during a tune-by-label channel change operation and entails a comparison of each character of the newly entered label and each character of the labels previously stored in memory until a match is found. In view of the memory read time requirements described above, such a search may undesirably add considerably to the total time necessary to effect the channel change.